A drug or therapeutic agent can be delivered to a patient by a medical device, such as, for example, a stent. Stents have been employed, for example, in the urethra, the ureters, the biliary tract, the cervix, the rectum, the esophagus, and blood vessels to relieve the pathological effects of constrictions occurring in these passageways.
Generally, drug-loaded stents are manufactured by blending the therapeutic agent with a polymer before forming the device or, alternatively, imbibing a drug into an existing medical device. The drawbacks of these methods are that the processing conditions may affect the stability of the therapeutic agent and/or the properties of the polymer and the finished devices. Blending the therapeutic agent with a polymer usually requires heating the mixture to temperatures that can negatively affect the therapeutic efficacy and/or the stability of the agent. Additionally, imbibing techniques usually employ a solvent for dissolving the therapeutic agent. Solvents, however, can be incompatible with some therapeutic agents and may compromise the solubility and/or therapeutic efficacy of the agent. Also, solvents can be incompatible with the polymer and affect certain properties of the medical device, such as, for example, rigidity or other mechanical properties.